Just a question for people who have completed the Japanese tree: How far will it get you? By this I mean how proficient will you be once you complete it? I have started it and I really like it so far. :)
This course is great for Survival Japanese, in that, it is useful to use for traveling. I believe they made this course in time for people who wish to travel to Japan during the Olympic Games in 2020.
With that being said, in my opinion, it is not enough to pass the JLPT (Japanese Language Proficiency Test) N5 level as Haelvateinn had suggested below, because the vocabulary list and grammar list is no where close to addressing all points to pass that level of Japanese.
However, this is a great way to introduce Japanese to someone in order to get a feel of the language before taking other supplementary courses or undertaking other methods of study.
It is also noted that this course is still in its infancy and perhaps down the road, improvements can be made to focus on the grammar, and vocabulary needed for each JLPT level.
I hope this has helped you.
From the May 18, 2017 Forbes article, right when the Japanese course launched: "In fact, the course includes all of the vocabulary and grammar needed to pass the JLPT N5, a proficiency test that I personally took two years of Japanese classes in order to pass."
I'm not very interested in doing the N5, so I have not compared vocabulary lists. But I have done the Duolingo course in its entirety, and my impression is that it covered pretty much everything (plus a bit more) that the first textbook in my real-life Japanese course did - and that took us more than a year to get through.